Process for coating cotton fabrics



y 1953 w. R. STANTON 2,639,966

PROCESS FOR COATING COTTON FABRICS Filed Oct. 18, 1950 3 Sheets-Sheet l3 (Own.

' I /m/em0r l/W/mm FF. Sfanfon By his altorneys y 26, 1953 w. R. STANTON2,639,966

PROCESS FOR COATING COTTON FABRICS Filed Oct. 18, 1950 s Shets-Sheet 2//7 Van for l V/ll/am R Sfcmfon By his attorneys y 6, 1953 w. R. STANTON2,639,966

PROCESS FOR COATING COTTON FABRICS Filed Oct. 18, 1950 v '3 Sheets-Sheet5 //7 van for W/Y/Iam R. Sfanfon By his attorneys Patented May 26, 1953UNITED STATES PATENT OFFICE PROCESS FOR COATING COTTON FABRICS WilliamR. Stanton, Penn, Wolverhampton, England; assignor to 'Textuffi'Limited, London, England, a British company Application. \October 18,1950,.Serial1No. 191L688 In Great Britain January 18, 1.949-

4' Claims.

It is known to pass a textile fabric, which may be wovenv or knitted,through an aqueous bath of cellulose derivative, for. example viscose,so that the fabric becomes coated with viscose, and then to treat thecoated fabric with a coagulating agent which. regenerates the cellulosein the viscose so that. a fabric coated with cellulose is obtained.Cellulose derivatives such as viscose which can be treated to obtaincellulose are hereinafter referred to as regeneratable cellulosederivatives. It is also known to treat the fabric before the coatingoperation with a View to reducing, the amount of air absorbed by thefabric; thus in. British specification No. 306,586, it is proposed toremove the air in. the fabric before the fabric reaches the.coatingliquid, by passing the fabric through a vacuum chamber immediately abovethe surface of the liquid.

British specification No. 611,275 describes and claims a process forcoating a knitted or woven fabric with cellulose by passing the fabricthrough an aqueous bath of regeneratable cellulose derivative and thentreating it with a coagulating agent, wherein the fabric is treated withlive steamimmediately prior to its immersion in the coating bath inorder to eliminate or to reduce to a minimum absorbed air and hence theoc currence of air bubbles or pin-holes in the final product.

In. carryin out the process according to the said British specificationNo. 611,275 it. is found that pin-holes may still sometimes result fromincomplete wetting of the fabric in the viscose bath when gases arisingfrom the decomposition of the viscose lead to the formationof. bubblesor pin-holes in. the final product. Furthermore, there; is a marked.tendency for minute blisters or: protuberances, as distinctfrompin-holes, to be=formed on the product.

It is the object of the. present invention to eliminate these furtherimperfections.

Thepresent invention comprises a process for (CL. SE -18) coating. aknitted. orwoven fabric with cellulose by treating the fabric with livesteam in order to eliminate or reduce to a minimum. absorbed air in thefabric, treating the steamed fabric in an aqueous bath, preferably a hotaqueous bath, so that the fabric is uniformly wetted out, passing thefabric through a. bath of a regeneratable cellulose derivative, treatingthe coated fabric with a coagulating agent and, during the coatingoperation, continuously withdrawing part of the bath of regeneratablecellulose derivative, passing the withdrawrr baththroughat'least onefilter and continuously returning the filtered bath to the coating-bath.The treatment of the steamed fabric with the aqueousbath mayconveniently be effected by passing the fabric through a hotwater bathwith the aid of guide rollers suitably placed for guidingthe fabric.through the bath; after withdrawal from the bath, the fabric may; beplaced between squeeze rollers to remove excess water and to smooth thefabric' which is then passed directly into abath of a regeneratablecellulosederivative. The treatment of the fabric with live steamfollowed? by thewetting out: treatment serves to. eliminatesubstantially completelythe formation of pin-holes in the final product.

Investigations which I have carried out: have shown that the blisters.in the final; product are. due to fibrils ofi' the cotton or othermaterial of the fabric; viscose tends to coagulate on these fibrils andthe aggregated viscose adheres to the fabric and; appears in thefi-nalproductas-minute protuberances or blisters. I have found thattheseblisters may be: eliminated. or. considerably reduced bycontinuously circulating part" of the viscose bath through. one or morefilters during thecoating operation, the filters serving to remove thefibrils of cotton and: the like. Filters consisting of? metal screens orfabrics having 15 to- 25- holes per' inchare=.particularly suitable foruse in thefiltering operation.

The fabric, after the treatment with. a: hot

aqueous bath in accordance with the invention:

may becooled, by passing it-throughthe air for a distance of" say sixfeet, and so allowing some of the water toevaporate, or by subjecting itto a cold water spray, and then passed into the bath of viscose orotherregeneratable cellulose derivative; The coating bath is preferablydivided by suitably placed vertical grids into three or morecompartments in which the grids help to restrain physically any bubbles,fibrils, aggregated fluff from the fabric or coagulated particles formedin the bath and so keep them away from the jet through which the fabricleaves the bath. The bath is preferably withdrawn from the compartmentnearest the jet and, after" filtering; returned to the same compart-11181117. The viscosebath may be cooled for example by means of water atordinary temperature (15 to 25 centigra-de) or by cooled brinecirculating in pipes submerged in the bath. (3001- ing the viscose inthis way tends to limit the aging. of the, viscose which otherwiseresults from the heating of the" viscose by the heated fabric passingthrough the' bath.

The aqueous bath preferably contains a wetting agent such as asulphonated long chain fatty alcohol in order to improve the wetting outof the fabric.

The aqueous bath may also contain a dyestuff which is substantive to thematerial of the fabric so that the fabric is coloured after the steamingtreatment. In this case the viscose or other regeneratable cellulosederivative bath may be pigmented preferably so that the coating willhave the same colour as the fabric; examples of dyes suitable for usewith cotton are the water-soluble dyes which are resistant to bothalkali and acid and are so unaffected by either the caustic soda in theviscose or the acid used as the coagulating agent. Chlorazol Sky Blue FF(Colour Index No. 518) and Diphenyl Red '7 BL (Colour Index No. 278) arespecific examples of such dyes. The aqueous bath may convenientlycontain from 0.1 to 0.2 per cent by weight of the dye.

The viscose used in the present invention is preferably a normal viscose'as used for threadmaking, that is -viscose containing about '7 to 8 percent of cellulose and about 6 to '7 per cent of caustic soda.

The knitted or woven fabric used in carrying out the present inventionmay be made from natural fibre such as cotton fibres or from syntheticfibres such as regenerated cellulose fibres, particularly viscose rayonfibres.

The present invention is illustrated by way of example in theaccompanying drawings in which Figure 1 is a schematic representation ofthe steps in the process for producing a cellulosecoated fabric,

Figure 2 is a vertical section through the steam chamber wetting outbath and viscose coating bath of the apparatus shown in Figure 1 but ona larger scale,

Figure 3 is a vertical section through the filtering apparatus forcirculating the viscose bath, also on a larger scale, and

Figure 4 is a section on the line 4-4 of Figure 3 but with only one ofthe tubes sectioned.

Referring to Figure 1, a fabric I is first passed through a steamchamber 2 into a bath 3 containing a wetting-out solution 4 and the wetfabric is then led into a bath 5 containing viscose or otherregeneratable cellulose solution 6. The solution 4 may contain adyestuff for the fabric I and the cellulose solution 6 may contain apigment. The coated fabric leaves the bath 5 through an adjustable slotI and is passed by means of a stenter 8 through an acid coagulant bath9. It is then washed free from acid in a water bath I and passed on asecond stenter I I through a drier I2. Knives I3 then cut off theselvedges and the finished fabric is collected as a roll I4. Throughoutthe operation, part of the solution is continuously circulated by a pumpI5 first through a screen filter I6, then through a cloth filter I! andfinally back to the bath 5.

Referring to Figure 2, the fabric I enters the steam chamber 2 through aslit l8 and both sides of the fabric are sprayed with steam from twoparallel rows of steam jets I9, 20. The steamed fabric leaves the steamchamber 2 through a second slit 2| and is passed into the wetting-outsolution 4, under rollers 22, 23 out of the bath and between manglerollers 24 and then down to a spreading roller 25 just above thesolution 6. The spreading roller 25 is of known construction with adiameter greater in the centre and tapering away towards each end, andkeeps the wet fabric from crumpling. The fabric passing from thespreading roller enters the solution 6 and is passed by means of rollers26, 21, 28 to the nip of a pair of rollers 29, 30 and thencehorizontally through centralising rods 3| to the exit slot 1 for furthertreatment as described with reference to Figure 1. The bath 5 isprovided with four wire screen 32, 33, 34, held in slots on the side ofthe bath 5; each screenconvenientlyhassixteen holes to the inch. Thescreens 32, 33, 34, 35, divide the bath 5 into three interconnectedcompartments 31, 38, 39. From the compartment 39, the solution 6 iscirculated continuously through the filter I6, the pump I5 and thefilter I1 and back to the compartment 39 by way of a pip 40.

The filter I6 is conveniently a wire gauze filter basket 4| (Figure 3)having sixteen holes to the inch. The filter I1 consists of an outercasing 42 with a top cover 43 in which are secured seven separate filtertubes 44 each of which communicate with a space 45 above the cover 43.The tubes 44 conveniently consist of an inner perforated tube 46, a wiregauze 41 having sixteen holes to the inch wrapped around the tube 46 anda fabric filter 48, consisting of an unbleached strainer canvas havingtwenty-two holes per inch, Wrapped round the gauze 41. The viscose isforced upwards through the filter tubes 44 into the space 45 and thenceback via pipe 40 to the bath 5.

In order to permit the passage of slubs through the slot 1 acounter-balancing weight 49 is provided, the weight being so adjustedthat while a slub in the fabric I can lift the top part 50 of the jet toenable the slub to pass through, the slot will immediately revert to thepredetermined width once the slub has passed.

The solution '6 may be cooled by means of a water jacket (not shown)around the bath 5 or by passing a brine solution through pipes (notshown) within the bath 5.

The invention is illustrated by the following examples in whichapparatus as described in Figures 1 and 2 was used.

Percentages are by weight.

Example 1 The wetting out solution used was a 0.15 per cent aqueoussolution of Diphenyl Red '7 BL at 80 centigrade, the solution containing0.01 per cent of a sulphonated long chain fatty alcohol as a wettingagent.

The viscose used contained 7.5 per cent of cellulose and 6.25 per centof caustic soda, was aged to a salt figure of 4.0, was pigmented with 9per cent of Monolite Fast Red 2 RVS (page 173 of Pigments by J. S.Remington, published by Leonard Hill, Ltd.) and 3 per cent of titaniumdioxide based on the weight of the cellulose, and contained 0.15 percent by weight, based on the weight of the cellulose, of a sulphonatedlong chain fatty alcohol. The temperature of the viscose bath wasmaintained at approximately room temperature (20 centigrade). During thecoating operation, viscose was continuously circulated through a sixteenmesh basket sieve and a twenty-two mesh unbleached strainer canvas asdescribed above with reference to the drawings.

The product was an all-red cellulose-coated fabric.

Example 2 solution containing 0.01 per cent of a sulphonated long chainfatty alcohol as a wetting agent.

The viscose used was the same as that used in Example 1 except that theMonolite Fast Red 2 RVS and titanium dioxide pigment mixture wasreplaced by a mixture of 4 per cent of Irgalite Blue KRV (Geigy ChemicalCompany) and 4 per cent of titanium dioxide based on the weight of thecellulose.

An all-blue cellulose-coated fabric was obtained.

Example 3 The solution used was a 0.15 per cent aqueous solution ofChlorazol Green GS (Colour Index No. 599:) at 80 centigrade, thesolution containing 0.01 per cent of a sulphonated long chain fattyalcohol as a wetting agent.

Thelviscose used was the same as that used in Example 1 except that themixture of pigments used contained 4 per cent of Monastral Fast Blue BVS(Journal of the Society of Dyers and Colourists, 1943, page 223), 5 percent of Monolite Fast Yellow GNVS (Journal of the Society of Dyers andC'olourists, 1943, page 223), 8 per cent of titanium dioxide and 0.25per cent of carbon black, based on the weight of the cellulose.

An all-green cellulose-coated fabric was obtained.

What I claim is: 1

1. A process for coating a cotton fabric with cellulose which comprisestreating the fabric with live steam in order to remove absorbed air inthe fabric, passing the steamed fabric through an aqueous bathcontaining a wetting agent suitable for wetting out cotton so that thefabric is uniformly wetted out, passing the wetted fabric through aviscose bath, treating the; viscosecoated fabric with a coagulatingagent,f and, during the coating operation, continuously withdrawing partof the viscose from the bath, passing the part so removed through atleast one filter to remove the fibrils of cotton in the viscose, andcontinuously returning the filtered viscose to the coating bath. 1

2. A process as claimed in claim 1 in which the aqueous wetting out bathis heated and the wetted fabric is cooled before it is passed into theviscose bath.

3. A process for coating a cotton fabric with cellulose which comprisestreating the fabric with live steam in order to remove absorbed air inthe fabric, passing the steamed fabric through an aqueous bathcontaining a wetting agent suitable for wetting out cotton and at leastone water-soluble direct cotton dyestuff substantive to the material ofthe fabric, so that the fabric is uniformly wetted out and dyed in thebath, passing the wetted dyed fabric through a viscose bath containingat least one pigment, the dyestuffs and the pigments being so selectedthat the cellulose coating has the same colour as the dyed fabric,treating the viscose-coated fabric with a coagulating agent, and, duringthe coating operation, continuously withdrawing part of the viscosebath, passing it through atleast one filter to remove the fibrils ofcotton the viscose and continuously returning the filtered viscose tothe coating bath.

4. A process for coating a cotton fabric with cellulose which comprisestreatingthe fabric with live steam in order to remove absorbed air inthe fabric, passing the steamed fabric through an aqueous bathcontaining a sulphonated long chain fatty alcohol wetting agent so thatthe fabric is uniformly wetted out, passing the wetted fabric through aviscose bath, treating the viscosecoated fabric with accagulating'agent, and, during the coating operation continuouslywithdrawing part of the viscose bath, passing it through at least onefilter to remove the fibrils of cotton in the viscose and continuouslyreturning the filtered viscose to the coating bath.

WILLIAM R. STANTON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,942,383 Dickhaut Jan. 2, 1934 2,378,186 Clark June 12, 1945FOREIGN PATENTS Number Country Date 280,262 Great Britain Nov. 15, 1927611,275 Great Britain Oct. 27, 1948

3. A PROCESS FOR COATING A COTTON FABRIC WITH CELLULOSE WHICH COMPRISESTREATING THE FABRIC WITH LIVE STREAM IN ORDER TO REMOVE ABSORBED AIR INTHE FABRIC, PASSING THE STEAMEDD FABRIC THROUGH AN AQUEOUS BOTHCONTAINING A WETTING AGENT SUITABLE FOR WETTING OUT COTTON AND AT LEASTONE WATER-SOLUBLE DIRECT COTTON DYESTUFF SUBSTANTIVE TO THE MATERIAL OFTHE FABRIC, SO THAT THE FABRIC IS UNIFORMLY WETTED OUT AND DYED IN THEBATH, PASSING THE WETTED DYED FABRIC THROUGH A VISCOSE BATH CONTAININGAT LEAST ONE PIGMENT, THE DYESTUFFS AND THE PIGMENTS BEING SO SELECTEDTHAT THE CELLULOSE COATING HAS THE SAME COLOUR AS THE DYED FARBIC,TREATING THE VISCOUSE-COATED FABRIC WITH A COAGULATING AGENT, AND DURINGTHE COATING OPERATION, CONTINUOUSLY WITHDRAWING PART OF THE VISCOSEBATH, PASSING IT THROUGH AT LEAST ONE FILTER TO REMOVE THE FIBRILS OFCOTTON IN THE VISCOUS AND CONTINUOUSLY RETURNING THE FILTERED VISCOSE TOTHE COATING BATH.